[simon@NV55C cg]$ gradle build
:generateGrammarSource UP-TO-DATE
:compileKotlin
w: The '-d' option with a directory destination is ignored because '-module' is specified
e: /home/simon/Code/cg/src/main/kotlin/com/github/simonorono/cg/lib/BitArray.kt: (69, 53): 'infix' modifier is required on 'rem' in 'kotlin.Int'
:compileKotlin FAILED
FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':compileKotlin'.
> Compilation error. See log for more details
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD FAILED
Total time: 22.704 secs

Here you can find the whole code. Is this a know bug or should I report it?

This is a known bug. rem was added in Kotlin 1.1.0, but the suggestion to replace it is incorrectly shown even for projects that use the 1.0.6 runtime. However, we do recommend you to update your runtime to 1.1.0.